Method of treating cast hollow ingots



Jan. 30, 1934. J. c. slEGLE METHOD OF TREATING CAST HOLLOW INGOTS FiledJan. 29, 1932 I-rM* w f NNN@ Patented Jan. 30, 1934 1 UNITEDl STATESMETHOD oF 'raEA'rmG oAs'r noLLow mco'rs Jacob C. Siegle, Youngstown,Ohio, assignor to The Youngstown Sheet and Tube Company, Youngstown,Ohio, a corporation of Ohio Application January 29, 1932. Serial No.589,563

8 Claims.

This invention relates to the treatment of hollow cylindrical ferrousbodies having irregularities and impurities in their inner surfaces andis particularly directed to a method of treating centrifugally casthollow ingots to smooth up their said surfaces and/or removesegregations of foreign material lying adjacent thereto.

When hollow ingots are cast centrifugally, the molten metal is pouredinto a rapidly rotating mold and the rotation of the mold continueduntil the metal is substantially solidified. As the centrifugal forceacting upon the molten metal urges it very strongly against the walls ofthe mold, material of less density than the metal and contained thereinis carried toward the center and may ultimately reach the inner surfaceof the ingot, wherein the interior surface of the finished ingot isusually quite rough. When ingots or pipes formedv in this manner areused as made, without further working of the metal; for example, whenthey are filled with concrete to form pilings, or the like, theroughened interior so produced may be of appreciable value in retainingthe concrete in the pipe, but when it is desired to work the ingot intorelatively thin walled pipes and tubes this internal 4roughness is adistinct disadvantage and coupled with the presence of the segregationstends to the production of defects in the finished articles.

The principal object of the present invention, therefore, is to providea method of treating hollow ingots whereby roughness of their interiorsurfaces and segregations of foreign matter incorporated therein may bereadily removed and relatively smooth interior surfaces of substantiallypure metal may be produced instead.

A further object of the invention is to provide a method of treatment offerrous bodies of the class described in the course of which thematerialforming the inner surfaces thereof is locally oxidized and therebyconverted into a relatively brittle scale, the subsequent removal ofwhich leaves a smooth surface on the interior of the body.

Another object of the invention is to provide apparatus suitable for theperformance of the said method and comprising in combination with aheating furnace in which the ingots are brought to desired workingtemperature, meansV operative to introduce an oxidizing uid into theinterior of the ingots as they pass successively through the furnace tothereby convert the inner surface metal and any foreign segregationsincluded therein into oxides which may be readily cracked or broken awayduring subsequent attenuation of the ingot or other working thereof in asuitable rolling mill or other apparatus.

Other purposes, objects and advantages of the invention will hereinaftermore fully appear or will be understood from the following descriptionof a preferred manner of performing the method by means of the saidapparatus, reference being had to the accompanying drawing in which Fig.1 is a diagrammatichorizontal sec- 65 tionof a heating furnace suitablyequipped for the practice of the method with a plurality of ingotsdisposed in its interior, and Fig. 2 is a diagrammatic fragmentary sideelevation of a skew roll piercing mill or like apparatus employed forworking the ingot and breaking off the internal scale after the furnacetreatment, a portion of an ingot in its passage through the mill beingshown in vertical section.

' The furnace F shown in Fig. 1 may be of any 75 usual type adapted forheating the ingots t0 proper working temperature, its walls being formedof refractory material such as fire brick or the like. Charging skids Cor other suitable means may be disposed adjacent the charging port P atone end of the furnace to facilitate introduction of the ingots, andspaced skids S may be arranged inside'the furnace to support the ingotsI as they are moved gradually and consecutively through the latter Whilethey are being heated. The ingot discharging apparatus at the oppositeend of the furnace comprises a pusher R which may be projected through aport P' into the furnace and successively into engagement with theadjacent end of each ingot as it reaches working temperature to therebyforce it axially outwardly through a port P" onto a. conveyor D or otherreceiving apparatus from which it may be carried by a crane or othersuitable conveying means to the apparatus provided for the next `ensuingoperation. The several ports are normally closed by suitable doors (notshown) in the ordinary way.

It will be understood that the traverse of'the ingots through thefurnace usually, and in accordance with my invention, progresses at arate suiciently slow to enable them to absorb the requisite amount ofheat from heated gases supplied to the furnace by any usual means (notshown) to raise them to the desired Working temperature' and that theingots are discharged one at aV time through the port P when they havereached that temperature, conveying means of any suitable type beingusually provided for moving the ingots along the skids S.

According to my invention I extend through the walls of the furnace,preferably near its exit end and thus relatively close to the conveyorD, one or more nozzles 1, two being generally preferred, whichrespectively project into the vfurnace and `terminate in-jets 2 atlongitudinally spaced points adjacent the path of travel of the ingotswhen disposed on the skids S and substantially in the -plane of theiraxes. Each nozzle has a longitudinal passage in its interior and isinterconnected with a supply pipe or manifold 3, through a valve 4, fromwhich compressed air, oxygen, or other gaseous oxidizing fluid from anysuitable source (notshown) is supplied. If. desired, a larger number ofnozzles than two may be provided and arranged in parallel `relation atsuitably spaced points and all connected to the manifold supply pipe 3,while additional like nozzles 1 may be respectively interconnected withanother manifold supply pipe 3 through valves 4 on the opposite side ofthe furnace as indicated in dotted lines in Fig. 1. Eachof the nozzlesas controlled by its valve is thus capable of projecting a quantity ofgaseous, oxidizing fluid into the interior of the ingot respectivelydisposed in alignment therewith on the skids Sl bores of the ingots,preferably as they approach the desired working temperature. .'I'hus,the usual heating operation required to-raise the ingots to thattemperature is in no way interfered with or modied, the oxidizing mediumbeing preferablyV introduced, as stated, as the end of the heatingperiod for each ingot is approached. However, in the preferred practiceof the invention, the quantity of the oxidizing fluid utilized is suchthat substantially the entire amount introduced is retained within theingot and the preferably neutral or slightly reducing character of theatmosphere within the main chamber of the furnace therefore remainssubstantially unaffected while the atmosphere within the individualingots is made highly oxidizing in character.

After the oxidizing fluid is introduced into the interior of the heatedingots through the jets 2 at the inner ends of the nozzles 1 by manualor automatic opening of the valves 4 and 4 when the ingots are inalignment with the nozzles, the oxidation of the material forming theinner walls of the ingots proceeds at a fairly rapid rate due to itsrelatively high temperature so that a relatively thick or heavy scalecomposed of metallic oxides and of any other impurities which may becarried thereby in the form of segregations is soon produced within theingot. Moreover, as the metal in the interior of the centrifugally castingots frequently solidiiies in small projections, it is apparent thatthe latter, if present, will also be substantially oxidized into scaleand that the metal underneath the scale will consequently be. relativelysmooth after the scale has been removed. Scale of this character isextremely hard but is relatively brittle and" may be readily crackedloose from the unoxidized metal of the ingot when the latter isattenuated or otherwise worked by suitable means during the subsequentoperations customarily incident to the formation of pipes and tubes fromhollow ingots.

Thus, for example, removal of the scale may be readily effected bypassing the ingot througha mill of the character of that indicated inFig. 2

vandthus comprising a pair of diagonal or skew rolls 5 of suitable shapeand a mandrelor piercing head 6 disposed therebetween. It is believedthe operation of this apparatus will be readily understood as it is ,notsubstantially different from` that of the ordinary diagonal or crossroll piercing mill, the working of the metal as the ingot passes l.

through the mill serving to break the scale loose from the inner wall ofthe ingot from which it can then be readily removed as a loose andratherfinely divided deposit by means of a blast of air or in any othersuitable-way. In the diagonal rolling referred to it is, of course, notnecessary to permanently change the form of the ingot by attenuation ofthe metal in order to break the'scale loose therefrom but as suchattenuation is generally effected on ingots of this character inaccordance with the methods of operation now in use for forming pipes ortubes therefrom, the scale removal will usually be carried outcoincidentally with and as a part of a rolling operation primarilydesigned to elongate the ingot rather than as a separate step directedto the removal of thescale alone. f l Y -I have found that ingots whichhave been treated as hereinabove described are substantially free fromundesirable projections or roughness on their interior surfaces and fromsegregations of foreign material and/or other impurities adjacentthereto, either or both of which, as iswell known in the industry,frequently cause seriousdefects in the finished tubes or pipes' if notremoved before the formation thereof from an ingot. Additionally, bysuitably controlling the amount of oxidizing fluid introduced into theingots in the furnace, the oxidation of their exterior surfaces is notmaterially increased beyondv the normal amount which occurs underordinary ably neutral or slightly reducingcharacter of the atmospheregenerally inthe furnace chamber. Y

Thus by my invention, I am enabled to produce smooth pipes and tubes ofhigh quality free from many of the defects which occur in pipesand tubesmade from centrifugallyfcast hollow ingots in accordance with themethods -iowjn use Aand by means of apparatus now employed for suchpurposes, but without appreciably" increasing manufacturing costs, sincethe apparatus employed is of relatively simple and inexpensive characterand requires but little attention for 1 its proper operation.

While I have herein described my invention with particular reference tothe preferred manner of practising my improved method by means ofapparatus of the character herein disclosed, it will be understood thata heating furnace of form ,or type .other than that to which I havereferred may be employed,and that changes in the design andarrangement-` of 'other parts of the apparatus and/.or in the vspecificmode of operation thereofin carrying lout 1the method may be made, if

and desire to protect by Letters Patent of the United States:

l. The method of preparing a hollow ingot for subsequent working whichcomprises the steps of heating the ingot to working temperature andduring such heating introducing into the interior thereof gaseousoxidizing fluid to form a scale, and thereafter working the ingot tofree the scale from the bore.

2. The method of preparing a hollow ingot for subsequent working whichcomprises the steps of heating the ingot to a predetermined temperaturein a substantially non-oxidizing atmosphere and prior to the attainmentof that temperature injecting into the bore of the ingot a gaseous iiuidadapted to oxidize the metal surrounding the bore to thereby form aheavy scale on the wall thereof. l

3. In a method of treating hollow ingots, the step of injecting agaseous oxidizing fluid into the bore of each ingot while the ingot isat a sufcient temperature to react relatively rapidly with said fluid tothereby form a scale, and thereafter working the ingot to free the scalefrom the bore.

4. The method of treating a hollow centrifugal- 1y cast ingot whichcomprises the steps of positively effecting oxidization of its interiorsurface only so as to form a scale thereon and thereafter working theingot to free the scale from said surface.

5. The method of treating hollow centrifugally cast ingots to removeinternal roughness and segregations-of impurities which comprises thesteps of successively heating the ingots .in a heating furnace to raisethem to a predetermined working temperature, injecting into the bore ofeach ingot a gaseous medium adapted to oxidize the metal surroundingsaid bore, then removing the ingot from the furnace, and finally workingthe metal thereof to crack oi the scale formed in the bore by saidoxidation.

6. The method of treating hollow centrifugally cast ingots to removeinternal roughness and segregations of impurities which comprises thesteps of consecutively heating the ingots in a heating chambercontaining substantially non-oxidizing atmosphere to thereby raise theingots to a predetermined Working temperature, injecting into the boreof each ingot while in the chamber a gaseous medium adapted to effectrelatively rapid oxidation of the metal surrounding said bore, removingthe ingots consecutively from the furnace, and finally working the metalthereof in such'manner as to break off the scale formed in the ingotbores by said oxidation.

7. The method of treating a centrifugally cast hollow ingot to removeinternal roughness and impurity segregations which comprises the stepsof heating the ingot to a predetermined working temperature in asubstantially non-oxidizing atmosphere and, while in said atmosphere,creating a strongly oxidizing atmosphere in the bore of the ingot tothereby oxidize the metal surrounding the bore and form a heavy scale,then removing the ingot from the heating zone, and nally working themetal of the ingot so as to crack.

said scale away from the wall of the ingot bore.

8. The method of treating a centrifugally cast hollow ingot to removeinternal roughness and impurity segregations which comprises the stepsof heating the ingot to a predetermined temperature, positively creatinga strongly oxidizing atmosphere in the bore of the hot ingot to therebyoxidize the metal surrounding the bore and form a heavy scale, and thenworking the metal of the ingot so as to crack said scale away from thebody of the ingot.

JACOB C. SIEGLE.

